This invention is related to a stable aqueous aluminum dispersion useful in waterborne coating compositions.
It is well known to add metallic flake pigments such as aluminim flake pigments into coating composition to provide the composition with metallic glamour. There are relatively few problems with the addition of these flakes into solvent based coating compositions but in waterborne compositions the aluminum flake tends to react with water and deteriorates the flake and can cause the evolution of gas. To avoid such problems, agents have been incorporated such as phosphate compound as shown in Backhouse et al U.S. Pat. No. 4,621,112, issued Nov. 4, 1986. Up until now, it has not been possible to directly formulate stable water based metallic flake dispersions that contain a relatively high solids level of metallic flake. The practice has been to formulate the metallic flake dispersion in a solvent base and then invert the dispersion into water. The direct formulation of a stable water based dispersion has not been accomplished.
This invention provides for the direct formulation of a stable waterbased high metallic solids dispersion that can be added directly to a waterborne coating composition or can be used to shade a waterborne coating composition to provide a desired color.